I wouldnt go to a shock collar before trying anything and everything else. Shock collars I find work when they are on however do not teach anything other then fear the collar. I have seen dogs behave when they know that collar is on and then back to there old habits the minute it is off. I would find a trainer who can work in other ways and methods then shocking them.
You do understand about DA right? have you started to crate train them at all? if not I would start there. You need to be aware when they are together , hopefully will never give a reason to seperate them but incase you do be prepared. Watch for triggers when they are together, added attention to 1 or 2 , if your wife is loving on her 2 and not him well there is a reason for jealousy. toys, food, treats, attention, over excitement all can cause fights to break out.
Mine play really loud and some are very vocal so knowing the difference in tone in your dog will help you know when play is not play, or if it gets to exciting you can step in and always calm it down, break them up , snap them out of that intense play.
Pit bulls are..... Beauty without Vanity, Strength without Insolence, Courage without Ferocity, and all the Virtues of Man, without his Vices.""